Latios

Latios [Latias in HG] will be roaming the Kanto section of the map as soon as you get the Magnet Train pass. Unlike the dogs though Latios will run BEFORE your turn if his speed is higher then yours. Routes 24 - 25 are good back and forth Routes to wait for him. Because of the pain of getting him to show up and also the fact he runs IMMEDIATELY I would use the Master Ball to just get him and get it over with. You can try to use moves like Mean Look that keep a Pokemon from running as long as your Speed is higher then Latios. If you are getting all the Legends at the end game then you probably do have him beat for Speed.

to clarify any confusion:Talk to this girl who tells you she lost her doll (can't remember where)Talk to the chubby guy at the pokemon fan club in Vemillion city to get it backWhen you exit, Steven Stone should tell you that Latios is roaming Kanto, but it should be in HoennAlso if you go to Silph Co. H.Q in Saffron City, Steven Stone will ask you if you had 3 stones in front of you, which one would you choose?Green-TreeckoBlue-MudkipRed-Torchic

I am having SSSSSSSSSSSOOOOOOOOOOOOOO much trouble just finding him. I haven't encountered him ONCE. I had 4 Master balls and I used them on Entei, Raikou, Lugia, and Ho-Oh. I think I should just get another because he is SSSSSSSSSOOOOOOOOOOOO hard to catch.